Non-invasive mechanical ventilation improves walking distance but not quadriceps strength in chronic respiratory failure

Background: In patients with chronic respiratory failure (CRF) nocturnal mechanical ventilation (NMV) confers increased exercise tolerance. The hypothesis tested in the present study was that the increased exercise performance is associated with increased quadriceps strength. Methods: In 28 patients...

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Bibliographic Details
Published in:	Respiratory medicine Vol. 97; no. 7; pp. 818 - 824
Main Authors:	Schönhofer, Bernd, Zimmermann, Christoph, Abramek, Piotr, Suchi, Stefan, Köhler, Dieter, Polkey, Michael I
Format:	Journal Article
Language:	English
Published:	England Elsevier Ltd 01-07-2003 Elsevier Limited
Subjects:	Activities of Daily Living Aged Exercise Test Exercise Tolerance Female Humans Hypercapnia Leg Lung - physiopathology Male Middle Aged Muscle fatigue Muscle, Skeletal - physiopathology Non-invasive mechanical ventilation Pulmonary Disease, Chronic Obstructive - physiopathology Pulmonary Disease, Chronic Obstructive - therapy Respiration, Artificial - methods Respiratory insufficiency Tensile Strength Walking Hypercapnia Respiratory insufficiency Muscle fatigue Non-invasive mechanical ventilation Exercise test
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Summary:	Background: In patients with chronic respiratory failure (CRF) nocturnal mechanical ventilation (NMV) confers increased exercise tolerance. The hypothesis tested in the present study was that the increased exercise performance is associated with increased quadriceps strength. Methods: In 28 patients with CRF due to chronic obstructive pulmonary disease and restrictive thoracic disease (post-tuberculosis-sequelae, scoliosis and obesity-hypoventilation) NMV was started. Before and after 2-month NMV the exercise tests, namely shuttle and 6-min walking distance, were performed. Furthermore, quadriceps strength was measured as the twitch tension elicited by magnetic stimulation the femoral nerve (TwQ) and the maximum voluntary contraction force (MVC). Results: After 2 months therapy with NMV there was significant clinical and blood gas improvement. NMV significantly improved the walking distance by approximately 18% but there was no improvement in TwQ or MVC, the data could exclude a 15% improvement in TwQ with 82% confidence. Conclusion: The strength of quadriceps does not change after 2 months of effective NMV in patients with CRF despite a marked increase in endurance time. Factors other than quadriceps strength account for the improved performance.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0954-6111 1532-3064
DOI:	10.1016/S0954-6111(03)00037-4